DD263648A1 - METHOD AND DEVICE FOR PRODUCING MICROWAVE PLASMES WITH LARGE EXPANSION AND HOMOGENEITY - Google Patents

Abstract

The invention aims to realize the advantageous effect of the non-thermal microwave plasma high chemical and / or physical material conversion rates to expand large-scale processing zones with great homogeneity. According to the invention, a method is specified for this purpose in which microwave energy is defined from a leading waveguide in a second waveguide and coupled out in a variable manner so that a homogeneous plasma is generated in the processing zone. The associated device provides a first waveguide, to which a second is coupled by known means and that the plasma chamber is coupled to the second waveguide. FIG. 2 {microwaves, decoupling, variable, waveguides, microwave plasma, homogeneous, large-scale}

Description

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Method and device for producing microwave plasmas with high expansion and homogeneity

Field of application of the invention

The invention serves the advantageous use of the non-thermal microwave plasma, with its high chemical and / or physical conversion rates, for plasma processing methods v with large-area substrates and large plasma halide in the plasma processing zone. Particularly suitable fields of application are the deposition of layers, e.g. Plasma polyols, hard coatings or semiconductor layers, the plasma etching and the physical surface activation · The suitability of the invention for the generation of laser plasmas should also be emphasized.

Characteristic of the known technical solutions

Non-thermal microwave plasmas for chemical and / or physical mass conversion exhibit discharge rates which are higher by about one order of magnitude compared with discharge plasmas produced in other ways. "They are thus particularly suitable for industrial use in the processing of bulk articles, especially large-area ones and / or articles to be coated continuously. The prerequisite for this is the presence of simply constructed, extended plasma sources. Depending on the physical properties of the microwaves (propagation capability on spatially exactly delimitable waveguides) is particularly suitable here

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The use of elongated, line-shaped, variable-length plasma sources accessible laterally, and if necessary parallel to each other, must be as homogeneous as possible along the sources. Moreover, deviations of the line from the straight line should be possible within certain limits also to be able to process curved objects.

The known solutions for the production of non-thermic microwave plasmas in the neutral gas pressure range between

1 3 10 and 1 (r Pa can be classified according to the type of coupling of the microwave energy into the plasma. A group of solution variants is characterized by the arrangement of dielectric discharge vessels in resonators or the use of resonators as discharge vessel (eg Fehsenfeld, F.). Instrum., 36 (1965) 294s DE-OS 311 725 2, DE-OS 260 693 7). The resulting plasmas are very much due to the resonance effect and the deraentspreohenden mode structures of the resonators inhomogeneous, if not scaled down to small volumes on the order of a few centimeters to a few cubic inches. For large volumes, mode competition and thus instationarity of the plasmas may occur. Changes in the plasma parameters shift the operating points of the resonators and bring about adjustment problems The advantage of the plasmas produced on this catfish is the relatively high achievable electron density (10 cm ^-1) ) and by the resonance effects facilitated ignitability of the plasmas. A further group of solution variants contains the various possibilities of arranging discharge vessels in closed waveguides (eg * Pehsenfeld FC et al., Rev * Sei * Inatrum * 36 (1965) 294; Gilgenbaoh, RM *, Am. J * Pays. 1984) 710} Zakrzewski Z., Czech J. Phys. B34 (1984) 105; Mejia, SR et al., Rev. Sei. Instrum. 57 (1986) 493).

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In this case, the dimensions of the plasmas are limited by the waveguide dimensions (at the industrial frequency of 2.4 GHz, the usual cross sections of H - mode rectangular waveguides are approx. 5 × 10 om), corresponding to the mode image of the waveguides is inhomogeneous and occurs with larger dimensions again fashion competition at ·

The electrical conductivity of the plasmas also makes it possible to use them as waveguides themselves. In devices called Surfatron or Surfaguide, the microwaves are surface waves on plasma columns produced by them in dielectric tubes with diameters in cm (eg Moisan, M. et al., Rev. Phys. Appl. 17 (1982) 707). The advantages of these devices are the small dimensions of the coupling devices in comparison to the length of the plasma column produced, which cause the conversion of the waveguide or Lecher waves into the plasma surface waves, the long lengths (up to 2m) and the almost complete conversion of the microwave energy into plasara energy. Disadvantages are the principle-dependent spatial dependence of the plasma parameters along the columns. Thus, these plasmas can hardly be used for technological processes in which the substrates to be processed are arranged alongside the plasmas. "A surfatron-like coupling device is disclosed by Kato and co-workers (Kato, I # et al., J Appl Phys. 51 (1980), 5312). The plasma (diameter 0.2 to 2 cm) supported by a quartz tube forms the inner conductor of a coaxial conductor. The last two devices are well suited for the generation of reactive flowing-afterglow plasmas Solution variants is the arrangement of discharge vessels in the field or stray field of antennas or open waveguide structures US-3663858 and US-3814983 or other radiating elements,

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e.g. Coupling holes, coupling soles and pins in waveguides, to name a few »

In the device of US-381 498 3 an elongate discharge vessel with dielectric walls is arranged in the field of a ladder-shaped, open delay line terminated with a matched absorber. A slight inclination of the line and the vessel to each other causes the compensation of the power sinking along the plasma advancing microwaves through enhanced coupling between waveguides and plasma * DE-OS 314 798 6 improved this arrangement by using two adjacent delay lines fed in opposite directions, which are slightly rotated about their axes so as to produce a common, even more homogeneous plasma * Duron staggered arrangement of the rungs of the two lines of the plasmas of the individual lines imitative influence of the conductor structure is reduced · With these An-orders the currently most extensive non-thermal microwave plasmas for Stoffwondiungszw corner realized ·

According to the cited prior art, all methods and devices have in common that a large-scale plasma zone can only be homogenized to a certain extent and that the once structurally fixed plasma distribution can no longer be varied. A parallel arrangement of several plasma zones is only possible to a limited extent because of the open structures then influence unchecked «It is also difficult to adapt a homogeneous plasma to non-planar substrates *

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Object of the invention

The object of the invention is to produce a hoo-reactive, non-thermal and homogeneous homogenous plasma with which advantageous physical and / or chemical conversion processes can be realized «

Explanation of the essence of the invention

The invention has for its object to provide a method and a device in which a Mikrowellenenergiestrbmung using waveguides and coupling elements for generating a uniform in the Bearbeitungsaone and großräuraigen plasma is exploited »

Erfindungsgeiii the object is achieved by a method that the microwave energy by means of a first microwave conductor and introduced from this coupled with known coupling elements in a second waveguide, which in turn is coupled directly to the plasma chamber, wherein the energy input in dio plasma zone defined in the longitudinal direction and variably adjusted such that the attenuation of the wool energy by the plasma and inhomogeneities due to the decoupling are compensated.

With this solution according to the invention, it is possible to vary the amount of energy that is introduced in the plasma zone in such a way that a homogeneously homogeneous plasma is present within the specific processing zone. This prerequisite for balanced chemical and / or physical plasma processes, ζ · Β a uniform layer formation · The substrate surface and thus the processing zone can be a

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be flat surface or other Oberfläohenformen, such as bends, have ·

In the case of larger substrates, according to the method, a multiplicity of such variable energy couplings into the plasma chamber can take place in parallel. In order to implement this method, a device is proposed according to the invention in which the wave energy is supplied from a source via a first waveguide to which a second waveguide is coupled in parallel one or more variably adjusting · ^{ 'bare coupling elements are present at the coupling point and the plasma space is coupled to the second waveguide · the first and second waveguide advantageously have the same line wavelength, since otherwise undesired wave superpositions occur · When using rectangular waveguides can be very Advantageously, the coupling wall be designed as a structurally common wall «

An advantageous coupling of the second waveguide to the plasma space is via the narrow side of the right-angle waveguide. With this solution, the plasma properties in the transverse extent can be favorably influenced.

A further embodiment may be formed such that the second waveguide encloses the first and the Piasinaraum externally coupled · The waveguides may be formed in a known manner as a waveguide, as a dielectric waveguide or dielectric filled with waveguide · It is also possible the second waveguide directly into the plasma as a microwave entry window · In this case, this second waveguide must contain a dielectric «

The most important advantages of the solutions according to the invention consist in a spatially concentrated,

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compact construction of the source and better plasma homogeneity along and across the source «. Furthermore, the length of the plasma zone can be varied during operation and it is thus possible to generate inhomogeneities in the plasma in a targeted manner. The concentrated structure facilitates the parallel arrangement of several sources for producing plasmas with a large transverse extent.

execution Beipiele

The invention will be explained in more detail below with reference to five exemplary embodiments. The accompanying drawings show in FIG. 1 the basic circuit diagram of the method, Pig. FIG. 2 shows a device with T-shaped hollow backbone.

Fig. 3 shows a device with rectangular waveguides, the

with the broad side abutting, FIG. 4 shows a device with two coupled rectangular waveguides,

5 shows a device in which the second waveguide is at the same time the microwave window and FIG. 6 shows a coaxial embodiment.

In FIG. 1, the block diagram of the method is shown sohematically.

Along a microwave conductor 1, which transports microwave energy in one or more stable modes (of the Lecher or waveguide or surface wave type) from a generator 3 to a matched absorber, microwave energy is converted into a second by means of suitably distributed adjustable coupling elements

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Coupled parallel waveguide, which is constructed so that there is at least one mode capable of propagation, which is attenuated by the plasma forming part of its boundary · This second waveguide is at its two ends duroh matched absorber 5 and 6 completed »These are preferably constant distance of the coupling elements with each other and their degree of coupling chosen so that sioh throughout the second waveguide duroh superimposition of the wave components each more coupling elements sets a very uniform Energiediohte «In this way, both the influence of duroh the decoupling decreasing Bnergieflußdiohte in the first waveguide as auoh the influence The discrete distribution of the coupling elements compensated and there is a very homogeneous over the length of the length of the length. · Lifting discrete coupling elements can be continuously distributed coupling elements, such as lange ··· · long waveguides in the direction of the absorber toward the absorber However, the advantage of the variability of the arrangement, its adaptability to altered plasma parameters, is lost or made more complicated by changing the setting of a limited number of coupling elements.

Embodiment I j The device according to FIG. 2 consists of two H..Q-mode |

Recoil waveguides with the same waveguide wavelengths, which are T-shaped focussed · The plasma forms on one narrow side of the coupling

Waveguide 2, in which a vacuum-tight i Window of microwave material 14 loading \

finds · By the special choice of the width of this;

Window allows the transverse expansion of the plasma and,

influence the electric field strength in the plasma · j

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The coupling between the B-fields of the two waveguides via coupling holes θ, in the middle. The hooks are fastened to the surface of the microwave guiding waveguide 1 guided thin, insulating suspensions 10, with the help of which they Zweoks setting the coupling damping in ''

The absolute values of the coupling damping, which can be varied, are determined by the dimensions of the coupling hooks (length and diameter) and the diameters ( ) of the coupling holes. "Duroh the use of waveguides, the mounting of Sohirmhülsen 11 at the ducts of the hook suspensions and the possibility of connecting the waveguide walls directly to the walls of a metal recipient, a high degree of safety against health-threatening microwaves can be achieved lick radiation become possible * 2 |

The essential features of this embodiment φ are the very high Homo 'in the near-window areas; the plasma Auoli in the transverse dimension and the time-independent, unambiguous polarization of the electric field f in the plasma (corresponding to the pattern of the current distribution on the waveguide walls). ; τ

Exemplary embodiment II V ₁ J

The decor after Pig. 3 consists of two H ^ _Q mode rectangular waveguides of the same dimensions, which have a common broadside «The distributed coupling is realized by coupling holes, in the middle of which are metallic conductive threaded pin« As in the embodiment I, the degree of coupling by the diameter of the coupling holes, determines the length and diameter of the coupling pins and their depth of immersion * The variation of the degree of coupling

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takes place via the change in the depth of immersion of the threaded pins seated in dielectric microwaveable hollow disks 12. On the second broad side of the coupling waveguide 2 there is again a microwave window 14 for coupling into the plasma.

With this annex, broader plasmas can be produced in the simplest way. However, the electric field strength and thus the plasma in the transverse dimension are inhomogeneous with the fashion image of the waveguides. When using flat waveguides can be particularly favorable curved) produce plasmas.

Embodiment III

In the device according to FIG. 4, two coupling ILQ mode rectangular waveguides 2, which have a common dividing wall 13, are coupled in phase with the broad side of the waveguide 1 leading the microwaves. The type of coupling is the same as in embodiment I. All three waveguides have the same dimensions * The two coupling waveguide 2 have a common microwave permeable window 14, behind which form two phases, which are already at a small distance from the window to a common in the transverse direction also superimpose homogeneous plasma. This embodiment is a particularly suitable basic building block for the production of planar, largely homogeneous plasmas.

Embodiment IV

In the device according to FIG. 5, the waveguide 1 leading to the microwaves is again a rectangular waveguide, at whose oine wide string the waveguide with a

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low loss dielectric (e.g., Teflon or quartz glass) filled second waveguide 2 is also coupled to the broadside. The dielectric also serves as a vacuous microwave window for the lietal recipient in which the plasma is created behind a longitudinal hollow seat in the second broad side of the second waveguide. To ensure the same wavelengths in both waveguides, the second waveguide is reduced in width corresponding to the value of the relative dielectric constant of the dielectric. By the use of flat waveguides shown here, of which the second waveguide is incorporated in the wall of a metal recipient 15, this embodiment can be extremely simple and compact and well adapted to curved lines of the plasma (eg Reζipienten walls) are adapted. The distributed coupling of the waveguide is realized similar to the embodiment II through holes in the common partition wall of the waveguide. In the middle of these holes are metallic threaded pins 7, which are in Gewindesackläohem in the dielectric. The variation of the coupling is made by turning in or out the pins. For this purpose, in the opposite side of the guiding waveguide cylindrical, small microwave-tight channels for performing appropriate tools or even holes 16 which can be closed during operation with metallic plugs. A disadvantage of this Ausführungsforra is slightly reduced power handling.

Embodiment V

This embodiment according to Pig. 6 consists of two concentric coaxial conductors, of which the inner coaxial line is the waveguide guiding the microwaves. The cavities of the waveguides are filled with a dielectric. The distributed coupling is through

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Holes 8 realized in the central conduit 17, in the center of which metallic grub screws 7 are located in threaded holes located in the dielectric, from the outer tube 18 to the vicinity of the inner conductor 19 · The degree of coupling is adjusted by adjusting the position of these grub screws. The required holes in the outer conductor can be closed by a threaded bolt of dieloktrisohera material with a metallic head if required ^. The plasma is produced on a longitudinal hollow seat 20 on the side of the || opposite the coupling points

Outer conductor · Due to this position of the plasma throws one

() Are achieved additional slurring the influence of discrete% coupling sites on the plasma longitudinal homogeneity · By using the coaxial technology, this training may ,, guide die in the dimensions kept particularly small · Furthermore daduroh a flexible structure of this embodiment for generating arbitrarily ge *-curved plasmas possible, but Sann: the lower electrical and thermal load-bearing capacity must be considered. · Also, within certain limits, a curvilinear arrangement of the plane on the outer jacket is possible «

Claims (10)

- 13 - P claim 1. Method for producing a microwave plasma mi '; large extent and homogeneity in the plasma zone to be used, in which the microwave energy is guided by waveguides and coupling elements in the plasma space, characterized in that the microwave energy from a first waveguide, which introduces the microwave energy, with known coupling elements in a second waveguide so defined variable is decoupled that the energy eint.-a / s; from the second waveguide into the plasma space in the longitudinal direction of the plasma zone forms a plasma with the desired homogeneity profile in the plasma zone to be used. 2. The method according to claim 1, characterized in that the coupling of microwave energy into the plasma chamber takes place several times in parallel, such that the multiple-forming plasma zones substantially unite to form a common planar plasma zone. Device for generating a microwave plasma with high expansion and homogeneity in the plasma zone to be used, characterized in that a second waveguide (2) is coupled in parallel to a first waveguide Π, which introduces the wave energy, in that at the coupling point a or a plurality of variably adjustable coupling elements (7) and (8) are present, and that the Plaamarauoi is coupled to the second waveguide. - 14 - P 317 4. Device according to claim 3, characterized in that the first and the second waveguide has the same line wavelength · 5. Device according to claim 3, characterized in that the first and the second waveguides are co-oscillating waveguides which have a common wall. 6 · Device according to claim 3, characterized in that the first and the second waveguide are rectangular conductors and the plasma space is coupled to the narrow side of the second waveguide * 7 * device according to claim 3> characterized in that the second waveguide surrounds the first and the plasma chamber is externally coupled · 8. Device according to claim 3 to 7, characterized in that the second waveguide is a dielectric wool conductor or dielectric filled waveguide · 9. Device according to claim 8, characterized in that the second waveguide simultaneously serves as a microwave entry window into the plasma. 10. A device according to claim 3 to 9, characterized in that a plurality of such devices are arranged in parallel, so that eich unite the individual plasma zones generated in the zone to be used to a substantially homogeneous plasma · For this .. ^ pages drawings